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Advanced Taiwan Ocean Prediction System

Tseng, Tsu-Lun - ALL News | 2018-11-12 | Count:23

Title: Quick Forecast of Tsunamis and Storm Surges

Abstract:

Usually earthquake scenarios are assumed to provide source conditions for tsunami hazard mitigation. Scenario analysis provides what might happen under some conditions, but we do not know if one scenario is more or less likely than the other. That is, changes beyond what current models project are possible. For example, more than 100,000 scenarios had been used in Japan before 2011. Unfortunately, the Tohoku Tsunami is not one of these scenarios. That is why a fast scenario-independent forecast of tsunami is desirable. For seismic tsunami, an economic forecast system has been developed to provide both offshore water surface elevation and inundation map based on the reciprocal Green’s function (RGF) of shallow water equations. RGF is based on pre-calculated matrices. Its efficiency and robustness is superior to real-time equation-solving, as has been shown in Chen et al (2015). Extending RGF approach to storm surges is not straightforward: Fault rupture is much faster than the water wave speed and hence the rupture process can be simply replaced by initial sea surface elevations. Thus, only the response to initial water level is needed. On the other hand, atmospheric forcing continuously contributes to the formation of storm surges and a much more complicated computation is involved. Besides, reciprocities of different Green’s functions are necessary. However, the RGF approach can significantly accelerate the forecast of offshore water level, and the computation process is simpler and more robust than real-time equation-solving,

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